Problem: Luis ate 4 slices of pizza. Nadia ate 5 slices. If there were initially 10 slices, what fraction of the pizza is remaining?
$\text{fraction of pizza eaten} = \dfrac{\text{number of slices remaining}}{\text{number of slices total}}$ Together they ate 9 slices, which leaves 1 out of 10 slices remaining. There is $\dfrac{1}{10}$ of the pizza remaining.